As long as a shield has hit points remaining, any damage done to the protected creature is dealt to the shield instead. A shield can absorb damage of virtually any kind, from physical damage types (bludgeoning, piercing, slashing) to energy damage types (acid, cold, electricity and fire), to force damage, to even most typeless forms of damage. Shields are even effective against touch attacks. A shield can never absorb more damage than it has hit points remaining, and any damage over that amount is dealt to the protected creature.

Only certain damage dealing effects can pass through a shield without being absorbed, such as a sonic effect, a gaze attack or psionic effects that allow a Will save. Line of sight and line of effect are unaffected by a personal shield. Nonstandard or conditional forms of damage such as from the reduced effect of a destruction spell or the corrosive effect of a rusting grasp aren't reduced by a shield.

Kinetic barriers are shields that only stop high-speed physical projectiles. The stopping power of a kinetic barrier is dependent on the speed of the object hitting it, providing a degree of deflection correspondent to the momentum of the object. The result is a shield that stops fast moving objects like weaponsfire but has no effects on slow moving objects, allowing the creature to interact with its environment without deflecting it.

Objects stopped by a kinetic barrier include high speed objects and projectiles. Weapons such as handguns and rifles, cannons and particle beams are stopped, but lasers, energy effects and other massless or incorporeal weapons are not. Melee attacks are not stopped by a kinetic barrier, nor are slow-moving ranged attacks such as arrows.

Certain machines possess shields that protect an area around them. As long as the shield has hit points remaining, it stops objects and energy outside it from passing through, like a wall of force, decreasing its hit points by the appropriate amount. Objects and energy coming from inside the perimeter shield can pass through unimpeded. Effects that can pass through shields can also pass through perimeter shields (like sonic energy).

If the damage caused to the perimeter shield by an area effect breaks through it, the area effect may continue beyond the perimeter shield if the area permits; otherwise it is stopped at the perimeter shield just as any other area effect does. In the case of an area effect caused by an explosive effect, like a fireball or an acid flask, the explosive projectile detonates upon impact with the shield. Regardless, the center of an explosive effect lies outside the perimeter shield.

The effective AC of the perimeter shield itself is 15 plus the deflection bonus it grants. Attacks originatig from outside the perimeter shield cannot directly target a creature inside it until the shield is down. Such attacks are resolved with the shield itself as the target.

Perimeter shields are projected as a spherical field around their source. A perimeter shield does not extend into floors or walls. The radius of the shield is listed in the object or creature's description. A perimeter shield blocks line of effect (except that of sonic effects) provided it has at least 1 hit point, but not line of sight.